In an X-ray generation apparatus of transmission type generating an X-ray by colliding (bombarding) electrons against a transmission-type target, X-ray generation efficiency is generally very low. When electrons are accelerated to a high energy level and are collided against the transmission-type target to generate an X-ray, about 1% or less of energy of the colliding electrons is converted to the X-ray and the rest, i.e., about 99% or more of the energy, is converted to heat. It is also known that reflection electrons are produced upon electrons colliding against the transmission-type target, but the reflection electrons do not contribute to the generation of the X-ray. Therefore, an improvement of the X-ray generation efficiency is demanded.
PTL 1 discloses an X-ray tube in which the X-ray generation efficiency is increased by arranging, between an electron source and a target, an anode member having a conical channel with its aperture diameter gradually narrowing toward the target from the electron source, and by introducing electrons to impinge against the target after being subjected to elastic scattering at a channel surface.